#197

Implement voice chat using Tox

There's a protocol for voice communication called Tox. It's fully peer-to-peer, end-to-end encrypted DHT-powered communication service, it doesn't require any additional servers. All you need to communicate over Tox is just one C library: https://github.com/TokTok/c-toxcore
By implementing this library into Xonotic we automatically get voice chat and contact list (easier to get together and play with friends), as well as some other interesting features that can be implemented using this library.